Environmental Problems, Their Causes, and Sustainability 1

Primary EnergySourcesHydrogenProduction TransportStorage UtilizationPhotoconversionSunlightElectric utilityWindElectricityGenerationElectrolysisCommercial/ResidentialBiomassFossil fuelsReformingVehicles andpipelineGas andsolidsTransportationIndustrialFigure 18-31 Solutions: hydrogen energy system used to run a sustainable hydrogen economy. (Data fromU.S. Department of Energy and the Worldwatch Institute)gas in a framework of water molecules called clathratehydrates or in tiny glass microspheres. Stay tuned forfurther developments from this research.Hydrogen is highly flammable and burns with aninvisible flame. But it may be safer than gasoline fortwo reasons. First, when this light gas is released itquickly disperses into the atmosphere instead of posinga fire hazard by puddling on the ground like gasoline.Second, metal hydrides, charcoal powders, graphite,nanofibers, and glass microspheres containing hydrogenwill not explode or burn if a vehicle’s tank is rupturedin an accident.Will Widespread Use of Hydrogen DecreaseProtective Ozone in the Stratosphere?Probably Not With with Careful Use ofHydrogenApreliminary study suggests that widespread useof hydrogen could decrease the concentration ofprotective ozone in the stratosphere over Antarcticafor a few months each year.In 2003, researchers Tracey Tromp and John Eiler at theCalifornia Institute of Technology published a paperthat sent shivers down the back of hydrogen proponents.On the basis of computer models, they projectedthat if hydrogen eventually replaces all fossil fuels, hydrogengas leaking from such a global system could riseinto the stratosphere, be oxidized to form water vapor,increase depletion of the ozone layer over Antarcticaduring part of the year, and allow more harmful ultravioletradiation to reach the earth’s surface.Most press reports failed to note that the authorsand other scientists gave several reasons why thisproblem may not be as serious as this preliminarystudy suggests. First, the authors’ model is basedon still poorly understood atmospheric chemicalinteractions involved in the hydrogen fuel cycle. Thisincludes the possibility that excess hydrogen in thetroposphere would be absorbed by soils or removedby reactions with other chemicals in the atmospherebefore most of it can reach the stratosphere.Second, the assumptions about leakage of hydrogenmay be much too high because of improved technologyand vigilance to reduce such leaks. Third, globalefforts are in place to drastically reduce ozone depletionin the stratosphere by 2050, mostly from chlorineand bromine compounds we have been puttinginto the atmosphere (more on this in Chapter 21).Since widespread use of hydrogen is not expected untilafter 2050, this potential threat would be greatlydiminished.What Are Some Possible Potholes in theHydrogen Highway? Getting DivertedBecause large-scale use of hydrogen is probably25–50 years away, we should not let its potentialdivert us from the immediate priorities of sharplyreducing greenhouse gas emissions by increasingfuel efficiency and encouraging the use of renewableenergy to help us produce hydrogen and phase outfossil fuels.Some analysts urge the United States to spend about$100 billion over the next two decades to spur thedevelopment of a renewable-energy hydrogen revolutionthat would be phased in during this century. Themedia hype about hydrogen can divert us from thefact that it will probably not be in widespread use for25–50 years.http://biology.brookscole.com/miller14403